# Thread: Is the perception of superluminal travel possible?

1. ## Is the perception of superluminal travel possible?

If we were hovering near the EH of a black hole shot a laser, then moved out into empty space, would the laser appear to be moving away from us superluminally? that is ... while we travelled from x to x + 1 y in time could we see the laser travel greater than 1 light year away from us?

The point here is to take into account the change in time dilation.

2. The perception of superluminal travel has already occurred, in observations of Supernovae. See here: http://en.wikipedia.org/wiki/Superluminal_motion

3. Originally Posted by Noclevername
The perception of superluminal travel has already occurred, in observations of Supernovae. See here: http://en.wikipedia.org/wiki/Superluminal_motion
Not sure if this is exactly what I am saying. But may be related and maybe can explain it differently than what Wikipedia suggests.

Basically saw we were near a BH ( hovering ) or some situation that had the ( general ) relativistic effects of a BH. Our time ( the time of the sun earth and maybe even the galaxy ) was warped significantly to that of the empty space between the quasar and us AND it was warped in our past compared to the space-time as we CURRENTLY percieve it.

Upon our escape into a different warpage of space-time we notice that the light has travelled WAY more than is possible travelling only at the speed of light. How can this be? However the percieved difference in distance travelled is because of OUR change of perception of time. If we were always an external observer then we would have seen it only travel at the speed of light.

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If we travel at nearly the speed of light to Bernard's star(say, 4 light years away) and notice that only 1 hour has passed on our watch, does that mean I travelled 4 LY in 1 hour? I haven't done anything impossible, but was 'apparently' moving at 8766 times the speed of light.

No it doesn't. Along with a change in time, there's a change in distance.

Are you 100% sure that time dilation due to gravity gives the same distances as no time dilation(empty space)? I'm not. Please re-examine time AND space within the context of GR.

5. Hubble's Law, v=HD (recession velocity is proportional to distance), is a theoretical result derived from the Friedmann-Robertson-Walker metric. v=HD applies at least as far as the particle horizon and in principle for all distances. Thus, galaxies with distances greater than D=c/H are receding from us with velocities greater than the speed of light and superluminal recession is a fundamental part of the general relativistic description of the expanding universe. This apparent contradiction of special relativity (SR) is often mistakenly remedied by converting redshift to velocity using SR. Here we show that galaxies with recession velocities faster than the speed of light are observable and that in all viable cosmological models, galaxies above a redshift of three are receding superluminally.
source: http://arxiv.org/abs/astro-ph/0011070

In other words: you can have galaxies receding at superluminal speeds because the galaxies are not moving away from us through space (which would be invoking SR) but rather the spacetime of the universe is expanding between us and the galaxies in question. Spacetime expansion is not limited to c. And we can see it.

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